IMO one skimmer would be best. Less cost overall, less space taken up and less work to maintain and clean. Dwell time is also important in skimming so a larger skimmer would give you higher dwell time. If you use ozone it becomes even more important.
For example 2 x 4"dia skimmer = 25 sq in of area while 1 x 8" dia skimmer = 50.25 sq in of area.
I could always sell you my used "Big Bertha" skimmer, it is 33" diameter and 8' tall.
Cheers,
Tim